Hong Kong, China (CNN) -- Hong Kong police said they had arrested two men in connection with an acid attack that injured six people last month.

The pair -- ages 18 and 23 -- were taken into custody on Wednesday for questioning in the attack, which involved corrosive fluid being thrown from a building in the Causeway Bay shopping area.

A man and five women were injured in the attack, according to police.

By Thursday, the younger man was released on bail, while the other was still detained, said Michael Kwan, information officer for the Hong Kong police.

Authorities did not say whether the two were being investigated in other similar attacks in Hong Kong, and it was not clear whether the attacks involved a group, individuals or copycats.

Police are offering rewards totaling HKD $1.7 million ($219,000) for information leading to arrests in recent acid attacks in five areas of Hong Kong, including the shopping district of Mong Kok.

Hong Kong Security Secretary Ambrose Lee on Wednesday said that if an object is dropped from a building and injures someone in public, the culprit could face six months in jail and a HK $10,000 ($1,300) fine. The throwing of corrosive fluid or manslaughter could result in life imprisonment, he added.